import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

import java.util.Iterator;

public class Stack<Item> {
    private Node first;
    private int N;
    private class Node
    {
        Item item;
        Node next;
    }
    public boolean isEmpty() { return first==null; }
    public int size() { return N; }
    public void push(Item item){
        Node oldfirst = first;
        first = new Node();
        first.item = item;
        first.next = oldfirst;
        N++;
    }
    public Item pop(){
        Item item = first.item;
        first = first.next;
        N--;
        return item;

    }

    public Iterator<Item> iterator() {
        return new ListIterator();
    }
    private class ListIterator implements Iterator<Item>{
        private Node current = first;
        public boolean hasNext()
        { return current != null;}
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }
        public void remove() {}
    }


    public  static void main(String[] args){
        Stack<String> s = new Stack<String>();
        while(!StdIn.isEmpty()){
            String item = StdIn.readString();
            if(!item.equals("-")){
                s.push(item);
            }
//            else if(!s.isEmpty()){
//                StdOut.println(s.pop()+" ");
//            }
        }
//        while(!s.isEmpty()){
//            StdOut.println(s.pop());
//        }
        Iterator<String> i = s.iterator();
        while(i.hasNext()) {
            String st = i.next();
            StdOut.println(st);
        }
//        StdOut.println("("+s.size() + "left on stack");
    }
}
